This application claims the priority of German Application No. 199 16 804.0, filed Apr. 14, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a device for adjusting a vehicle head support and a method using such a device.
A device of this kind and a method of this kind are disclosed in German Patent document DE 34 27 466 A, wherein a pyroelectric detector, which responds to the thermal radiation of the passenger""s head, is disposed approximately at the highest point of the head support. Starting from a rest position with the head support retracted, the detector receives the thermal radiation of the head and runs upward until it receives no more thermal radiation. It is then at about the same level as the passenger""s vertex. Due to an appropriate arrangement it no longer receives any thermal radiation in this position. The head support is said to be thus correctly adjusted. It can easily be recognized that such a device is extremely imprecise and does not assure an exact setting of the head support height essential to the proper operation of the head support.
The invention addresses the problem of creating a device of the kind referred to above, in which, with little effort, a precise adjustment of the head support is possible, and of offering such a device by which this adjustment is performed.
The invention solves this problem by providing a device for adjusting a vehicle""s head support to the position of a passenger""s head, with a sensor arranged in the head support to recognize the head position, characterized in that the sensor contains two condenser plates which are arranged one over the other and are part of a condenser, in which the passenger""s head acts as a dielectric. A method using such a device adjusts a vehicle""s head support, characterized in that the height is varied starting from a rest position with the head support retracted until the increase of the sensor signal of the one condenser plate takes place simultaneously with the decrease of the sensor signal of the other condenser plate.
The special advantage of the device according to the invention consists in its insensitivity to the distance of the head from the head support. Even if the head is not in contact with the head support, the signal delivered by the two condenser plates remains the same in its relation. On account of the simple and inexpensive design and great insensitivity to temperature, the result is a sturdy and reliable device for setting the height of the head support.
The use of two condenser plates in connection with a car seat is known in itself. Thus, in U.S. Pat. No. 4,796,013, the two condenser plates are arranged in the seat or seat back and adjacent to the object (passenger), so that it is known whether the seat is occupied. Any safety systems, such as an airbag and the like, will then be deployed only if this is actually the case.